Observations on the displays, menstrual cycles and sexual behaviour of the “Black ape” of Celebes (Macaca nigra)

The behaviour of a captive group of Celebes “Black apes” has been studied in order to describe the repertoire of visual displays and to gather quantitative data on menstrual cycles and sexual behaviour. A comparison of the displays of the Black ape with those of other Old World monkeys indicates that its behaviour is closest to that of Macaques and baboons. This lends support to the view that it should be included in Macaca , rather than being placed in a separate genus Cynopithecus.